Question

. An athlete completes one round of a circular track of diameter 200 m in 40 s. If he continues to run, what will be the distance covered and the displacement at the end of 2 minutes 20 s respectively?​

Answer 1

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• Total time = 2 minutes 20 seconds

⟹ 2 × 60 seconds + 20 seconds

⟹ 120 seconds + 20 seconds

⟹ 140 s

Now,

• In 40 s, the number of rounds completed =1

So,

• In 140 s, the number of rounds completed =
• $\frac{1}{40} \times 140 = 3.5$
• Calculation of distance covered in 3.5 rounds

The diameter of circular track is given to be 200 m, so the radius (r) of the circular track will be half of it, which is -

$\frac{200}{2} = 100 \: m$

Distance covered in 1 round = Circumference of circular track = 2πr

⟹ $\pi = \frac{22}{7}$

⟹ $2 \times \frac{22}{7} \times 100$

⟹628.57 m

⟹Distance covered = 628.57 × 3.5 m = 2200 m

• Calculation of displacement in 3.5 rounds

⟹ The athlete makes three and half round (3.5 rounds) of the circular track. Now, if the athlete start from a point A, then after 3 complete rounds, he will reach at the same point A. And when the athlete again start from point A and make the remaining half round he will reach point B. So, that this placement will be equal to diameter of the circular track which is 200 m.